Willst du was trinken?
Do you want something to drink?
The sentence you gave is in fact a yes-no question (I assume that is what you mean by closed question). That is the reason why the verb is in first position.
In the given case, was is not a question word (interrogative pronoun) but an indefinite pronoun with the same meaning as etwas. Note that wer, ...
First you may want to note that this usage of "ablegen" isn't very common. As a native speaker, I actually had to check whether you may have meant "anlegen". A more common or contemporary version of the sentence would be
Natürlich legt er es nicht im geringsten darauf an, den Herrn von Prackwitz zu ruinieren.
The example sentence that ...
The German word for workaholic is Workaholic. We use this English word as a foreign word in German context.
7 Anzeichen dafür, dass Sie ein Workaholic sind
Zum Tag der Workaholics: Pro und Contra der Arbeitssucht
Warum es alles andere als sexy ist, ein Workaholic zu sein
Other synonyms are used less frequently:
Your sentence is entirely correct because of something called scope (Skopus, although that article is both a bit technical and not a good introduction to the concept). The idea is that nur can only restrict what occurs after it. Because abends appears to the left of nur, the interpretation only in the evening is excluded.
A simple example of scope in ...
Does my sentence express this clearly? I'm worried it might instead mean that the office is only open on Thursday evenings and no other time, which is not true.
Yes, your worries are justified. As expressed it is a bit unclear. Also Abends doesn't give the reader a clear timespan.
Id rather use a literal translation, e.g.:
Die Öffnungszeiten des Büros sind
Wie Sie sagen, habe ich nicht gearbeitet.
is clearly preferable since only with that word order it is one truly transposable compound sentence:
Wie Sie sagen, [so] habe ich nicht gearbeitet.
Ich habe [so], wie Sie sagen, nicht gearbeitet.
Ich habe [so] nicht gearbeitet, wie Sie sagen.
So is the implicit reference point of the relative clause wie Sie sagen....